Introduction

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Turkey Earthquakes (1915-2021) Data Set

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The “Turkey Earthquakes (1915-2021)” data set utilised in this study was obtained from Kaggle, in which it comprises of all the earthquakes with a magnitude greater than 3.5 that took place in Turkey and nearest areas from 1915 to January 2021.

The main source of the data is from the Kandilli Observatory and Earthquake Research Institute (KOERI), which specialises in the research of earthquakes.

The data set contains 15 variables, as explained in the table below. However, not all of the variables are utilised in this study, as they are chosen according to the analysis to be carried out.

Objectives

This study has three main objectives as follows:

1. To identify the trend of earthquake frequency, average magnitude, average depth and correlation between earthquake frequency and average of magnitude.
2. To determine the earthquake occurrences, spatial distribution, and temporal patterns in different cities.
3. To comprehend the nature of earthquake magnitudes by exploring and contrasting magnitude types in order to learn more about their features, variability and interconnections.

Plot 1

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Bar plot has been used to identify the trend of frequency of earthquake over time. Based on the plot:

• 13 events of earthquakes that have frequency that ranged from 1-9

• Highest frequency was in 2020 with 934 events recorded.

• 6 events of earthquakes that have frequency more than 500 which was in year 1999, 2005, 2011, 2012, 2017, and 2020.

Plot 2

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Area plot has been used to identify the trend of average magnitude and average depth of earthquake over time. Based on the plot:

• The highest average magnitude was in 1942, where the average magnitude was approximately 5.65 with an average depth of 26.13km.

• The lowest average magnitude occurred in 2009, with a magnitude of 3.72 and a depth of 14.09km.

• The light earthquake intensity where the magnitude is less than or equal to 4.9 spans from 1960 to 2021, displaying a range of average magnitudes from 4.45 to 4.83 and depths from 19.20 to 45.11 km.

• The moderate earthquake intensity with magnitudes greater than 4.9 and less than or equal to 5.9 covers years from 1915 to 1963, exhibiting average magnitudes from 4.92 to 5.65 and depths from 9.33km to 62.50km.

Plot 3

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Scatter plot has been used to identify relationship between frequency and average magnitude of the earthquake. Based on the plot:

• The correlation coefficient between the frequency and average magnitude of earthquakes is -0.7805606, indicating a negative correlation.

• As the frequency of earthquakes increases, the average magnitude tends to decrease, and vice versa. This has been supported by previous study as well.

Plot 1

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The word cloud visualises the earthquake frequencies in different locations of Turkey and its neighbouring countries.

-The larger the word, the higher the frequency of earthquakes in that location.

-Out of the 95 locations in the dataset, nine places are outside of Turkey, including Ege Denizi (Aegean Sea), Suriye (Syria), Gurcistan (Georgia), Irak (Iraq), Iran, Ermenistan (Armenia), Kibris (Cyprus), and Azerbaycan (Azerbaijan). The remaining locations belong to Turkey.

-Earthquakes occur more frequently in Akdeniz, Manisa, Mugla, Van, Kuthaya, Kahramanmaras, Denizi, Elazig, Burdur, Ankara, Bingol, Balikesir, Malatya, Izmir, Erzurum, and Canakkale.

-Akdeniz has the highest earthquake frequency.

• Akdeniz is the coastal region along the Mediterranean Sea in Turkey (Kurtulus et al. 2018).
• This region experiences a high frequency of earthquakes due to its location in a seismically active zone (Kurtulus et al. 2018).
• This area exhibits complex tectonic behaviour influenced by the faults of the Dead Sea, Eastern Anatolia, and Cyprus (Kurtulus et al. 2018).

-Ege Denizi (Aegean Sea) is the second-highest earthquake frequency.

• The most recent earthquake occurred in the Aegean Sea is on 30 October 2020 (Cetin et al. 2022).
• This earthquake produced a tsunami and resulted in 118 fatalities (Cetin et al. 2022).

Overview of Magnitude

-The word cloud does not provide information about the magnitudes of the earthquakes.

-However, Turkey and its neighbouring countries are situated in seismically active regions, where earthquakes of various magnitudes can occur.

-Therefore, it is crucial to visualise the earthquake clusters based on their magnitudes to gain a more comprehensive understanding of the seismic activity.

-The magnitude of an earthquake is measured on the Richter magnitude scale, which is a logarithmic scale used to gauge the amplitude of seismic waves generated by the earthquake.

-Here are the categories of earthquakes based on their magnitudes (The Associated Press 2012):

• Minor Earthquakes (Magnitude 0-2.5): Generally not felt but recorded.
• Light Earthquakes (Magnitude 2.5-5.4): Often felt by people but rarely causes significant damage.
• Moderate Earthquakes (Magnitude 5.5-6.0): Can cause significant damage to buildings.
• Strong Earthquakes (Magnitude 6.1-6.9): Can cause significant damage in populated areas.
• Major Earthquakes (Magnitude 7-7.9): Can cause widespread damage over larger regions.
• Great Earthquakes (Magnitude 8 or greater): Can cause severe damage to communities.

Plot 2

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The earthquake clusters are visualised through an interactive map.

-Three earthquake clusters.

-The left circle has the greatest number of earthquake events.

• Located on the Eurasian plate, the African plate, the Aegean Sea plate, and the North Anatolian Fault Line (NAF) (Earthquake Hazards Program 2023).

• The movement between the Eurasian and African plates is against each other, exerting pressure on each other (Demirci 2023).

• The NAF line is one of the fastest-moving and most active right-lateral strike faults in the world (Demirci 2023).

• It is 1400 km long and runs from the east of Turkey to the west of Turkey and ends at the Aegean Sea (Comfort et al. 2023).

• Provinces and cities included Gallipoli, Marmara Sea, the Gulf of Izmit, Adapazarı, Duzce-Bolu, Gerede, Merzifon, Suluova and Erbaa, Niksar, Kelkit Valley, Erzincan, Erzurum, Varto, Van, Canakkale, Edremit, Bursa and Iznik (Demirci 2023).

-The central circle has the least earthquake events, with a 988 number of earthquake events.

• The locations within this cluster are still in close proximity to the fault line and the Eurasian plate (Earthquake Hazards Program 2023).

-The right circle recorded 6992 earthquake events.

• Located on the Eurasian plate, the Arabian plate, and the East Anatolian Fault Line (EAF) (Earthquake Hazards Program 2023).

• The opposing movements of the Eurasian and Arabian plates create intense stress, increasing the likelihood of earthquakes (Demirci 2023).

• The EAF, a strike-slip fault line located in eastern Turkey, further contributes to seismic activity (Demirci 2023).

• Approximately 1000 km long and runs diagonally across Hatay, Osmaniye, Gaziantep, Kahramanmaras, Adiyaman, Elazıg, Bingol, Mus, Erzincan, and to the NorthAnatolian Fault Line (Comfort et al. 2023 and Demirci 2023).

Plot 2a

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The interactive map visualises the selected top 30 earthquakes based on magnitude, with the colour of the circles representing the magnitude.

-The darkest-coloured circle indicates the largest earthquake magnitude recorded in Turkey, measuring 7.9 on the Richter scale, which occurred in Erzincan.

-The second-greatest magnitude, measuring 7.7, is occurred in Gaziantep and Akdeniz.

• The difference of 0.2 in magnitude between 7.9 and 7.7 has released approximately 1.995 times more energy.

-The third-greatest magnitude in Turkey is 7.6, recorded in Kahramanmaras and Turkiye.

• The difference of 0.1 in magnitude between 7.7 and 7.6 has released approximately 1.412 times more energy.

Plot 3

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The gif animated scatterplot visualises the distribution of the earthquakes based on magnitude over time for the top 10 locations. -The top 10 locations are Akdeniz, Denizli, Ege Denizi, Izmir, Kahramanmaras, Kuthaya, Malatya, Manisa, Mugla, and Van.

• In 1926, Akdeniz experienced a powerful earthquake with a magnitude of 7.7.

• In 1948 and 1957, Akdeniz measured two earthquakes with magnitudes 7.2 and 7.1 respectively.

• In 1970, Kuthaya registered a magnitude of 7.0.

• In 1976, Van encountered a strong earthquake with a magnitude of 7.5.

• In 2011, Van experienced another earthquake with a magnitude of 7.2.

• In February 2023, Kahramanmaras experienced a earthquake with a magnitude of 7.6.

• Death toll surpassing 50000 people, particularly 45968 confirmed deaths in Turkey and 7259 confirmed deaths in Syria (ReliefWeb 2023).

-Once an earthquake of at least 7.0 magnitude occurs, the subsequent earthquake events exhibit reduced magnitudes below 6.

-This decline in magnitude signifies the release of stored energy from the previous seismic event.

Introduction to Magnitude Types

Limitation of the Data set

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• The moment magnitude, Mw, variable has many missing values.
  
• The other magnitude types are complete with all 17370 instances, but Mw only has 26.74% of its data available.
• Drop Mw and focus on the other four magnitude types.

Plot 1

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A correlogram of the magnitude types is simply a visual representation of the correlation matrix.

Non-significant correlation

• Mb and MD
• Correlation is also almost zero, showing no correlation between one another.
• Indicates that different shaking durations may occur during earthquakes with identical body wave amplitudes.

Highest correlation

• Mb and Ms, valued at 0.6192.
• When an earthquake has a high magnitude according to Mb, perhaps it will most likely display high amplitudes for Ms. 
• Does not imply a causal relationship, just that they have consistent patterns.
• This strong positive correlation could be due to the same fundamental aspects of the earthquake event influencing both magnitude estimating techniques, such as amount of energy released.

Negative correlation

• ML and MD, valued at -0.34.
• Shorter shaking durations are more common in earthquakes with larger seismic wave amplitudes, usually waves at a particular station.

These connections can help with further research and interpretation of the data, such as finding out what causes the correlations and what this means for estimating the size of earthquakes.

Plot 2

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This line graph can reveal the temporal fluctuations in magnitude values for each magnitude type.

Each month shows similar patterns of a downward trend.

• Seismic activity is a natural event that varies by increasing and decreasing over long periods of time.
• Technological advancements cause instruments to become more sensitive and thus accurate in estimating magnitudes.

Extreme peaks and troughs

• In the earlier years in April and September, the magnitude values except for duration are low.
  
• Peaks can be seen in January of the early years and July around the late 1950s.
• This shows how the earthquakes intensities vary over the long run.
• Sometimes there are not so many earthquakes happening and sometimes they occur with a big impact.

Body-wave, local and surface wave magnitudes start to fluctuate tremendously in the 1980s.

• Body-wave magnitude values are higher compared to the others at this point. Larger body-wave magnitudes may imply a stronger amplitude and energy release associated with the body waves.
• Duration magnitude is higher in the early 2000s. Higher duration magnitude values imply the occurrence of earthquakes in the early 2000s that have a longer duration of shaking.
• The local magnitude values show an interesting and clear upward trend towards the end of the plot. Higher local magnitudes could portray stronger ground shaking at the local site, meaning a higher energy release by the earthquake or it could have happened closer to the station.
• Evolving seismic network and monitoring practices.
• The GEOSCOPE network and the Global Seismographic Network (GSN) were developed in the 1980s, where even vibrations as small as the size of an atom could be documented digitally (Ringler 2022).

These scales all provide authorities with different insights in assessing the potential damage the seismic activities could bring.

Plot 3

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Depth is the distance from the location of the earth where the earthquake originates and the surface of the earth.

As there are different types of earthquakes, namely shallow, intermediate or deep ones, relating them to the different magnitude types will provide the relevant authorities with insights on the energy release mechanisms, enabling them to further refine their models.

• All four plots show similar patterns, being clustered mostly around a depth of less than 50 km, with a magnitude of 3.5 to 5.
  
• The surface wave magnitude values however are a little higher, around 4 to nearly 6, with the biggest Ms value going as high as 7.9 with a depth of 20km on 26 December 1939 in Erzincan.
• This event also has high MD and ML value of 7.2, and MB value of 7.1.
• The earthquake that left 30000 people dead and damaged thousands of buildings is said to be one of the worst earthquakes to ever happen alongside the recent Turkey-Syria earthquake of 2023 (Firstpost 2023).
• The slightly higher Ms values coincide with Plot 2 where even though the values have similar trend before the 1980s, the MS values can be seen to slightly overcut the others. This suggests that the earthquake produced more powerful but slower seismic waves that travelled across the surface of the Earth.

Most earthquakes tend to be shallower and quite a number of these events also have higher magnitudes than those events with a larger depth.

Logically speaking, shallower earthquakes are nearer to the earth’s surface and can have more intense impacts on the area. Therefore, shallow earthquakes with larger magnitudes are bound to cause more damage.

It is important to keep in mind that the magnitude value and depth of the earthquake can collectively determine the severity of the potential impact.